XV: Save for next event. Much better variety.
XI: Probably worth a pull, especially if you didn't for the last banner.
V: Worth 2 pulls, imho.
VI: Again, worth 2 pulls.
DU: Eh, far enough away and only really need 9 mythril along with the 16 from the DU to pull.
II: eh, not a common realm, but if you have mythril leftover from V and VI then yes.
4 events = ~1 month (Lets say 35 daily mythril).
4 events = 52 mythril
That right there puts you over 4 pulls and closing in on a 5th.